I. Field of the Invention
The present invention relates generally to relief valves, and more particularly, to a relief valve with improved means for varying the opening pressure of the relief valve.
II. Description of the Prior Art
There are a number of previously known relief valves. These prior known relief valves typically employ a housing having an inlet which is fluidly connected to a pressurized fluid line of a fluid system. At a predetermined pressure, the relief valve opens to permit fluid flow from the inlet on the relief valve housing and to an outlet also formed on the relief valve housing. Such relief valves are used with fluid systems to prevent excessive pressure build up in the fluid system. Otherwise, such excessive pressure can undesirably damage the fluid system and/or its associated components.
These previously known relief valves, however, all suffer from a number of common disadvantages. One disadvantage is that the relief valve housing, usually a casting, is not only expensive but oftentimes requires complicated mechanical and fluid connections to the fluid system. Moreover, such relief valve housings must be pressure tested to insure their safety and operability.
A still further disadvantage of these previously known relief valves is that the valve assembly itself is manufactured to a preset opening pressure rating. Since the opening pressure of the valve assembly itself is not adjustable, an entire line of relief valve assemblies must be manufactured and stocked in order to accommodate different opening pressure requirements. Moreover, if a different pressure opening is desired for a given relief valve application, the entire valve assembly must be removed and replaced with a new and different valve assembly.
A still further disadvantage of these previously known relief valves are that they are unduly complex and therefore expensive in construction. Moreover, such relief valve constructions oftentimes have fluid restrictions formed therein which can create unduly high pressure parts and thus require expensive heavy duty construction.